An end mill in which a plurality of outer peripheral cutting edges has different helix angles is known as being able to prevent the deterioration and the like of surface finish accuracy due to so-called chattering vibration since vibrations generated at an end mill body during cutting cancel each other out between the outer peripheral cutting edges having the different helix angles. Such an end mill is disclosed in, for example, Patent Document 1 in which the pitches between the outer peripheral cutting edges in a circumferential direction of each thereof are equal to one another at a range between one third of a cutting edge length from an end of each outer peripheral cutting edge, which is located at a rotational direction side of the end mill, and a central portion of the outer peripheral cutting edge, thereby preventing a width in a circumferential direction of a cutting chip discharge flute from being excessively narrowed at the end of the outer peripheral cutting edge.